776C85 is a potent inactivator of DPD, the first enzyme in the degradative pathway of 5-fluorouracil (5-FU). Pretreatment with 776C85 has significantly increased the bioavailability and reduced the pharmacokinetic variability of oral 5-FU tablets in animal models. It also increased the antitumor efficacy of 5-FU and increased the therapeutic index of 5-FU by up to six-fold. Based on these data and on promising preliminary results from phase I trials, it is hypothesized that combination 776C85 and 5-FU may be effective therapy. The combination also appears to be desirable for patients' safety and compliance. This study is designed to determine the bioequivalence of each strength of the combination 776C85/5-FU tablet to the separate 5-FU and 776C85 tablets used in clinical trials to date. This is a randomized, open-label, 3-way crossover study.